<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

        .wrapper {
            padding: 20px; 
            margin: 20px;
            /* 阴影 */
            box-shadow: 0 0 10px rgba(0,0,0,0.2);
            /* box-shadow 动画过渡 */
            transition: box-shadow 0.2s;
        }
        .wrapper:focus-within {
            box-shadow: 0 0 15px rgba(0,0,0,0.5);
        }

    </style>
</head>
<body>
    <div class="wrapper">
        <input type="text" />
    </div>

    <div style="width: 50px; display: inline-block; outline: 1px solid red;">
        <div style="background-color: antiquewhite;width: 100px;">
            <div style="">
                123
            </div>
        </div>
    </div>
</body>
</html>